Differential coordination means that there should be a certain gap between the upper and lower protective appliances in the network in the setting of the electrical action value. When a short circuit or overcurrent fault occurs at a certain point in the network, whether the protective appliance is a circuit breaker or a fuse Both the protective device and the protective electrical appliances can act selectively according to the pre-defined sequence of actions, and no leapfrog action is allowed, and the accidental power failure is limited to the minimum range.

(1) Differential coordination of protective electrical appliances in the low-voltage main switch cabinet. The power supply reliability of the protection appliances in the low-voltage main switch cabinet should be placed in the main position to ensure continuous power supply. Since the low-voltage protection appliances are close to the distribution transformer, it is required to be compatible with the protection characteristics of the high-voltage fuse on the primary side of the distribution transformer. Cooperate with the subordinate electrical appliances to achieve full selective protection.

(2) Differential coordination of protective electrical appliances in the terminal distribution box. The terminal distribution box is directly connected to the electrical equipment, and it is required to cut off the circuit as soon as possible or even instantaneously in the case of a short circuit or a ground fault. The low-voltage protection appliances in the terminal distribution box should be equipped with short-circuit and ground fault protection, and the end of the line does not need to be equipped with short-circuit protection, but according to the needs of the connected electrical equipment, install control appliances or install overload protection appliances for them.